Carrier-wave communication



Decn 25, 1928.

J. w. scHMlED CRRIER WAVE COMMUNICATION Filed Jux'le 29. 1922 /m/en/b/f A James [f1/Schmied Patented Dee 255.19281.

JAMES w. scrutini), OE WEST. ORANGE, NEW JERSEY;AssreNonrTOfwEsrEnNEEEQ i i -TEIC COMPANY, INCORPORATED, OENEW Yon'mf N. Y., ACOEPOEATION OENEW,

I YORK;4

1 This invention relates' `to `methods "of transmission l and systems for carrying. lthe methods' into effect and is particularly eX- emplified in a radio system for two-wayk l iment ofv'secrecyfinto radio communication, i

communicationv between A twoY distant points.

In a Vprior systemzf incoming high-fre-V quency carrier waves'are comloinedf'wlthy energy ofY the locallyA transmitted "carrier wave frequencyto produce annintermediatefrequency wave which is detected'or otherwiseutilized toreproduce thefsi'gnal;V 'Such a systemghas numerous advantages among' whichl are a' high degreeofselectivity, good amplification of received signals,V and full opportunity to'each ofV twofipersonsY Com-v municating'over the system'to'break in on each otherat any time if'theysoldesire,

Cil

Although 'all lthe features *ofthe present 'invention'. are not limited` initheir application to systems of the kind just described, one object of ther present'iuventio-n is .to adapt lthat type Ofsystemto'operate Yin accordance with `the principle..Offfvpartial orV complete suppression of `the'l unmodulated Vcarrier component, The method ofunf` modulated carrier component suppression-1s described in U.' SlpatenttoCarson,fSerial No.'1,34 3,306, granted'June 15,19207y The' `"present vsystem utilizes suppression fof the 'unmodula'ted carriercomponent, but it willvbe understood in `connection with Vthe following description that the unmodulated "carrier component maybe partlyV suppressed or may he as completely -suppress'ed'ua'slpossible. -In this latter respect the 'system'is'f an improvement upon thoseiin which itfis lio correct value.

essentialfto the operation thata small portion of the energy jof thepnnmodulated 'carl krier frequency isftransmittedw `A further ,ob ect lsto 'provlde means-'for supplying anunmodulated component of the f c intermediate carriervfrequency'l of" large f energy at each` station and tormaintain the" frequency of the Venergy thus'l supplied at lthe A feature of the present invention is that all the carrierfrequency waves'in'cluding the waves is therefore accompanied loya'simul-L taneous Avariation' of equal' percentagein all the other waves owing to `thefactthattheyf pr'essioi'n-y ofjthev urnnodulate'd component of-V 'i the mev y mated; ,carrier Wave' 'fit' .isi essential-1' that thfe'junmod reintroduced at" tl1`e receiver" J Y. Y t

'Where successive detection attire receiver final .stage vof detection.-

Vthe system. c From -thesebase frequencyfosf as hereinafter describedtf" 4 6.0i l K'I'n Yrado telephone'systeins employing supf Y i,

lated'Cmponentdshouldxlje f Y, :il:

is .employe-d the unmodnateaearne-r@qinlponent .may be introduced before th'egfrst n stagefof detection-orlat any time'before the two stage'spf detectinlareem ployeditis advantageously introduced'i'a'san intermediate f'requ''eri/eyl Qunmodulated ,cai-f f f j; rier cwafter the first and ibeforelthe f second stage ofjdetection, An"essentdfeatre'in 75 n .anyrjcase 'is thatrthelfrequncy O'fth'e- "un-1),: i l

,lrwillalted'carrier,icomponent-whichis'A ,i11-

.troduced be correct, "i.l,e.','f itmust coincidef COIHRHQH fwhih would 'be present at g that ,801- vpozintkhad Vytheca'rri'erY notubeensuppressed-f" quency, toset i' all' the "carrier 'frequencies' in cillations` both intermediate frequency i los'- cilllatlons f andy principal` carriei'I frequency osc1ll`at1ons* are'derived harmonie ''genj-V eration Th' principal ,Carrier nave-pro# lduced Aatthisf'station'is modulated'fin acc 'i i' fl 'ance with both base frequencyoscillations .I and outgoing signals. Y ,Incomingli "carrierA waves: received' fat'this,,stationvr "are-,"c'oml 'fhieh they differl'i'nffrequency, `totproduce; 1 't linterrmefdiate frequencygwaves whichfmay K1A be combinedwith lthellocally producedfijni "termediate' frequency. waves to yieldthe inn-51004 AComing'signal.

each refote station'itheiwave'- 'from the masterfstation'isr detected to duce 'baseafrequency oscillations and fr"o1n fthsejbase frequency oscillations areydeloi 'f livedf intermediate Y f requenc'y oscillations l- 5 f 'and principal carrier;oscillations;toihe usedfri respectively forfreception andj transmissl diagram of a typical yformofstaticr'iV B wliichjis adapted to communicate withva station such as the station A; andFig. 3 isa diagrammatic illustration iof an arrange-V p ment for varying the frequency of p the frequency setting generator.

' Y"In the drawing, use is made of conventional indications ofthe Ywell-known three,

Velectron discharge amplifier withoi'ithowever, showing complete Vcircuits associated with' these Vdevicesl The manner of connecting up the complete circuits is well-known. This (indicates that electron discharge de'- Vices of theftype indicatedare preferred formswof means ,for performing thel func-V i tions described. VHowever, vany equivalent circuits 3 is impressed upon lanotherV har-Y deyices suitable for performing theV Same functions may be u tlhzed At the station A (Fig. V1) provided a master generatoror frequency setter 1 which Vproduces waves assumedin'Y the present iii-- stance to have a frequency. of 5,000 cycles Vper second. lnthisspeciflcation, the term frequency V.will be i'itilized to indicate Y ficycles per second.V

Y V'llhesou'rce 1iiiipressesfwaves haviii'gfthe freq'uvencypof 5000 cycles upon a harmonic? producer 2 the vfunction of which. is to'produce frequency components which are liarnonics 'of`5000 cycles. Such harmonic pro-f ducei's are known' in the 'prior art and in one form usually consist of oneormoreelectro'n discharge tubes with suitable vauxiliary v'elements A suitable harmonic producer is edY November 13,1919. j Y y Y 1n the present insta-nce, theharnionic producer is designed Vto pro'ducefin its output circuit a current componentiwhich is the Ashown i'nBritish'Patent No. 131,426, grant- V`20th harmonic of 5000cycl'e's, viZ`,.100,000 cycles, which is selected"from'other'accom- Ypanyin'g Vcomponents by a Ysuitable*system :ofi selectivecircuits;3.

In the present spe'ciflcation',YVv isunderstood that the selective circuits 3' may V:be

forming the vnecessaryfseleetion.`

000 cycle component, aft'erselecti'on bythe monic producer ctoproduce current of the tenth; harmoniclof 100,000 cycles, viz 1,000,- 000 cycles. The current of the' lastrnained A'frequency isV selected byk suitable lselective circuits15',fampliiied in a thermionic amplifier Y6, and, afterr passing through selective cirscribed in UfSfp'at'entto Carson, Serial No.f

1,343,806, granted June 15, 1920. Also impressed' upon this "circuit are waves of speech frequency from a telephone circuit 8.

1 .The sourcevljalso supplies energy tothe inputof althermioiiic unidirectionally c'onducting device@ whose output circuite'is also coupled tothe input circuit of the modulatingsystemf, The modulating system is ad- Vjust'ed to suppresspartor all of the unmodu 1 lated carrier component. Unbalancelof the lat-oi' tubes than the other.V In practice absolute balance is difficult to attain.

The inode ofcperation with theunmodulated component only' partly suppressed will first be described andthereafter willbje: described an. optional method, With'the unmod- 'ulatedi componentY wholly suppressed. Thev output currentfioml the modulatorV thus comprises 'a current modulatedr'in accordance .witlispeech :and alsoV modulated in diating antennaV 8Y may, be tunecljfto selec- 'tively radiateone side band of the modulated wave more efficiently *than the other* Uu accordancewith current of 5000 cycles.' The side band, ort may 'radiate both side bands equally well.

Thereceiving apparatus of thecStationgr4 includes' a Vreceiving vantennaf), `which receives carrier waves having :af frequency of Y 1,000,000 cyclesradiated. from theaiitenna" 8, and carrier waves having frequency of 900,000 cycles-radiated from station B, here- ',inafter described, or from a station of similar nature. A

Y The trap circuit I10 be tuned to discriminate against the, current of frequency lof 1,000,000cycles so tliatthe energy of` this Yfrequency entering the receiving'papparatus Yis reduced to, an ainount'sucli 'that' it hears V`a reasonable 'relation tothat'i'elceived from` the station B.' This is notlto say, however,

that'theenergyentering the receivingappa-l fratus. from the anteima 8 is to be reduced amplitude toan amount veopual'to thatA reinay be desirable, under'vcertain circuini moretimes `as 4much `energy enter the receiving system ofthe station'A from its local transmitter as isreceived from station *Thev current.y energies of 900,000 cycles and 1,000,000 cycles frequency `will'loe understood to consist ofi'a relatii'elyA smaller negligible unmodulated component Y together with one 4or two sidebands resulting from modulationinaccordance with speech and modulation in (accordance with current `ef 5,000cycles frequency'. These currents in- Ich' Y l Y, p fceivedufrom therernote (station B,since it" band filters or Aother-circuits capable oflperf stances, to have as'lmuch as `one hundred or tion in"thefor1n of sidetfone together With The signals in transitare ,thereforebased upon a carrier Wave from'vvhich Ythe `untheconversation of lthe person ,at the station A VWith whom yheis conmiunicating.

V.It will be-noted thatV allV carrier frequencies,Y both `principal andintermediate, Vat

',each. of the stations A and Bare derived` from source l. Thisvinsures that any change froccurring many one ,of Vthese carrier fredescriptiOn. o l u ,Y A special mode ofV operation, however, Alends itself fto theintroduction of an eie'ment of secrecy, whereby persons having.ordinaryV quencies is accompanied by an equal per- V centage 'change in all of the others.

The mode of operation'of this system Will,r

be readily understood from the preceding receiving apparatus will not be able tof inter- -cept and receive messages readily. "v'lhisV specialmode Will nowbe described. Let it be supposed that the generator' l 1nstead of generatinga constant fr equency'of 5,000 cycles is caused by the use of any convenient means to undergo a slight-variation in frequency. This variation m frequency. may be cycllc or may occur at irregularY `in#` tervals. Vinasmuch as the frequency variaby means of a small conductive body `moving.l Vinthe `neighborhoodof the oscillator L VSee 'Fim f The V5,000cycle source il consists, for eX- ample, of a thermionic generatore carefully shielded Y from magnetic, electrostatic, and

other externalV disturbing infiuencesfby a shield b of conductive' material.-1 VThe frequencyV determining element `is. the usual ftune'd circuits. MountedV Withinthe shield,

adjustably adjacent the tuning condenser,

' isf an electrically driven, selffwinding clock.

The pendulum p of this clock, as it swings to and fro adjacent the tuning condenserd,

900,180 and the current of v 100,000V cyclesy f f causes a small variation in effective capacity of thercondenser. Other means for causing the small frequency variation mayy be Vemployed.

For causing irregular..v small frequency] Y variations along thin magnetic Wire e, such f A- as a telegraphone Wire,'may be made 'ofdifnv lferent permeability in yvarious part's'of its length and `may Vbe Vcaused to pass slowly adj acent the tuning,Y coil of` the 'oscillatorlto vary.' the effective `inductance Vof the coil-by small amounts. 1. l Y

'Suppose by Way thaty the current produced by; thev source-1l variesb'etweenOO cycles and-5,001 cycles,

thatfis, it undergoes aftotalfvariation Vof l/ 50th-of 1%, then all the othercarrer fre@ 60' quencies in the system Willzund'ergo a similar variation of 1/50th of-1%. Fo'11-example, the current of 1,000,000 cyclesitvill vary bewill vary between 100,000'and 100,020l1.; Y' Y `103 `W'illfbe suif'lcient to takeV care of this. Will be understood, of course, that the design fof all the selective Vcircuits of thesystem will `:be appropriately modiiiedwhen the carriers @modulated com onentfis larvel su ressedvWhichcarrier Wave is varying' Voverya total' range of 200 cyclesinthecase Aof messages transmittedfrom station A, and ,over Vaf range. of 180 cyclesin the case-of messages doing V is increased ,oWingvto the fact that *the messages transmittedfrom-the station A to the station Bare transmitted ongone carrier Wave and those from stationxB to the' station 'A Yare vtransmitted onanother carrier Wave. These .Waves undergo the same percentage vvariation but. diferent absolute variation'sl' The difiiculties inthe Way of intercepting both the messages Without the V`use ofl a receiving system involving practically all the -essentialelements ofboth tionis asmall onel it vmay be brought-.aboutYV interceptthe messages'. Thediiiculty ofsostationsand B or their equivalents Will therefore be I considerable., Hoyvevergffthe InodeA of Y operation' in` which the control frequency isj varied Willgiiot prevent recep-` ,tionwith the systems of, stations A and Br as described.' The .variation Lof all they frequencies Will interfere` very little With Width of the transmission bandof the `filters 11 and 111 and theselective circuits 3 and It are causedy to undergo variations of freeV quency for secrecy ,or other.1V purposes. 1 .i Y

VItwillbe obvious that source 1` can be utiiceives on a differentsetofl carrier frequenf liyed as a frequencyjsetter for afplurality Y `of stations B,`each ofvvhichtransmitsand re- '1155' cies. Various harmonics ofthe' A source 1' may be used forl signaling overtdiffere'nt channels. A t thef station A, additional channels or vduplicate setsof apparatus may be utilized to communicate With various remotefstations suchV Vas the station The intermediate carrierv yfrequenciesof the various stations may-be the samelor different, but, ofcourse, i

the principal carrier Vfrequencies must differ jif several m-essages ;areto be transmitted simultaneously. l

A convenient manner of varying the source'1.,is.to cause itto generate at 5,000 cycles per second for about one halfsecond andy then cha-nge V,tol-'5,001 Vcycles perl second 'alternate half vsecondsf In addition to producingdesirableresults by intention-1.

allyvarying' the frequency of the 5 source f1 over la small range;k the presentl system` is admirably Vadapted toy operate Well ffsmall cliangesin frequency of the source l .occur l'at' irregular intervals andffi'om v unprevent` pendedclaims..Y

What is/claimed is:A A .fr l; The method 'which' consists in transf.

mittingfrom"each of two 'stations'to'f'the'r (l Vrotlier on principalv carrier Waves, receiving saidWavessimultaneouslyatthe receiverof... Y .y n Y ing from a mastercontrol Wavea carrier frei each `station and demodulating ea'ch -vvitli the other', selecting the j dem(")dulation prod yNJ ucts corresponding to the difference frequency of Vsaid carrier Waves, I demodulating said products, witha'r'einforcing Wave'jof,

frequency equal to.A the v'differenceof said carrierh` frequencies,v Yand derivingl saidv 'car-l rierV Waves andys'and reinforcing-Wave Vfrom the same/source.V

In va 'two-Way Eradio communieation'v systemA having atfeach Vof .two terminals aj receiver adapted'toreceive and combine en` Y ergy of an outgoing carrier Wave with "the i energy of an mcomingicarrier Wave to `pro-V duce an auxiliary carrier Wave, the y"method of .controlling and maintaining 1`Xed relationships amongst-said Waves `vvlii'ch'comprises 'deriving all of 'sai master 'control Wave.

3. In a two-Way radio'y ycommunicationy l system 'having' at each of tWo"-t`erminals a "receiver adapted to receive'and combine energy of anoutgoimgV .carrier Wavel With'thel energy of an; incoming carrier Wc ve to .produce an auxiliary carrier Wave modulated vby vthe signal to be received,means for gen-l erating at one terminal Va control vfrequency and deriving therefrom a carrier frequency,

`means for transmittingsaid control Y* fre'r quency on said carrierwave tothe other ter? minal, `means thereat for detecting said 'coni-V trol frequencyand for producingtherefromv a secondV carrier frequencylmeans at'both ofv said terminals for deriving from the control frequencyY v'auxiliary Waves of YfrequencyV equal to the'dil'erence ofthefcarrierfre-V q u'encies7 and meansto combine'v'saidJauXiliary Waves With the aforementioned signal modulated auxiliary V Waves 'to' yield; Vthe signal. 7

4. A carrier Wave Vcommunication'systen'i comprising tvvo stations.havingV meansl fon tran'smittingv ya modulated carrierA Wave .and each having means for receivin'giand comf bining energy of. its lownoutgoingicarrier Wave With the incomingcarrier,Wave-.toproi duce an auxiliary "carrier Wave modulated.

by signals from4 eachstation' andfa singleV control frequencyfthe .method of receptioii" .70 Which 'comprises simultaneously receiving a VV`common .patli'fan incoming' carrier Wave n and fan outgoing carrier Waveiof different 'Waves'. With 'each other;

gaccording.; to low frequericvt signals, jsiniul-I outgoing andan inconnnggcarrief waive, delv modulating: said v.received Waves v'vlith` veach j -'.modulation' p roduc'ts, and subsequently,-

.l between two stations'Wliiclif comprises de- Waves from a f .low to radiate, 'deriving Vtherefrom a` f'z'arrierv the control vvaveand derivingtlierefrom differing Vin frequency; amount .equal to the: intermediate frequency; modulating *the Wave and 'ani incoming signal* modulatedflw v5.',111 a radiosignaling-gf.lsystemginfvvliiclrfV 'they carrier Waves i are 'cl'erived from aV master frequency, 'demodulating said, received Y' selectinggthe differ- A 75. y ence frequency demodulation'.products, subffv sequently "demodulating said V`productsfwith afrein'forcing Wave, and"` alsopderiving saidf` 7 reinforcing .'Wavey from# said "master fre-. so

uency.

.between two stations Vwhich Acmnprises Y der'v-.

quencyiwave and' anV intermediate.frequencyf y 'Wave y at eacli'rstation carrier' Wavesftss;

differing in frequency byan amount c orre-Y spending to -a `frequency abovethe range of audibllity, modulatingvthe'.,carrierfwaves Vta'neously g receiving in al common?. .p

ath.:- anvr 90.

other, selecting. the diiference ,frequency 4demodulating said product'sjwith.- vone oflsaidl 95.v

intermediate frequencies.; l

l 7./Thejfmethod Y of radio commun cation ff riving vfromv a `master control" frequency d acarrier frequency Wave and .anintermedi- 1Q ,Y ate frequency vsrlaveat each station;saidcar-` .-f rier Waves differing in .frequency andlsaid intermediate .Waves having .ai lfreouiemcy f 4 frequency-*Wave and ani-intermediatefrequencyfwave, modulating `the carriervvaFve. V.With the control Wave,V and radiating-thef. modulated carrierwave, receiving themodu- 0 i Ylzit'ed carrier "y -Vvvave, detectingl and. selectingy secondicarri'er wave anda second intern/nef.tV v diatejfre uenc Wave saidintermediate frecarrier-'Waves according signals, simultaneously receiving., an- Voutgoing L carrier? auxiliarycarrierfrequency which would re v y t Vin accordance-with; an arbitrary law over,

WaveV deniodulating and. selecting the'` dif'- feience frequency products,` and' subsequently'` `deinodulating said'rproducts with' one offs'a'id station a carrier Wave for ltransmission and reception andan auxiliary carrier. Wave for Vreception7 comprising means whereby each stat-ien radiates a single modulated Vcarrier Wave with V`the* uninodulatedi component largely suppressed, means at each stat-ion for` cen'ibining said radiated waves, and means v for supplying at each of said'stations alargeI coinpone'ntV` Wave of a frequency identical with the unmodulated component` of the sult from the combinationof the small remaining uninodulated carrier components `of lsaid radiated waves.`

' 1G; n a two-way VradioY communication systenileniploying carrier Waves of different frequencies varying in, anarbitrary manner for transmitting. in two directionsiwth'e niethod wliiclircoinprises receiving at each Vstation and combining an outgoing carrier Wave with anincoining Vcarrier Wave to proy 'the l energy of an incoming carrier' waveto` duce an auxiliary carrier wave niodulatedfby signals,Y deriving Vsaidcarrier waves lfrom a` inaster control; wave, and varying in an 'arbi A H ingzsent from eacli of theltwovstations, coin-V bining such intermediate frequency wave at:

trary manner the frequency ofV said control wave. ,v

11. Ina' two-wayV radio communication system-'having at each oftwo terminals. a`

receiver adapted Ato receive and' combine energy of an outgoing carrier wave with produce an auxiliary carrier v-'wavef the ,inethod vof securing secrecy which comprisesderiving said car-rieur waives from a Vinaster 4control Wave of low frequency; and varying quency variationA of said carrier 'Waves'does not exceedithe frequency vrange of audible v speech, 1

l2. In a two-wayV radio` signaling systeinr having at each terminal frequency selective transmitting. andV receivingy apparatus and in whichleacli receiver isadapted to receive and combinevenerg'y of an outgoinglcarrier Wave .with the energy of an incoming carrier'wave to producev an auxiliaryV carrier wave,"A the inetliod of producing secrecyj which 'comprises derivinglsaid: carrier Waves? from a,

master-,control ,wave 0f-lowfrequency and varying. .the frequency ofV said control' 'waveY a. frequency range such thatl the resultant-` frequencyY variation o .said` carrier waves does not' exceed the limitsof selectivev trans- Y 'rnis'sionandi reception. V

12. The method ,ofWave.transmissionIcom` Uprising transmitting messages-ias inodula tionsY of"r twoY carrierwaves of@ Tdifferent` fre*- qiiencies in the two opposite directionslcomf `bining Yat `reach?. ofi two -jstationsthe transniitted and. received carrier: waves to 'pro-1 duce: at Veach station` anlinterinediate fre quency Wave modulated-by theinessage loe-A each stationjwith' an",iininodulated` waveof th'ersame frequency' to -V reproduce the nies-` sage, and deriving both Athe carrier waves, 

